#|Hello All,
I'm attempting to ensure that shapes drawn onto a canvas don't overlap. In
order to do so, I attempted to use region% objects.| #
#|Takes two rectangles, and tells whether they overlap as regions.|#
(define overlaps?
(lambda (rect-a rect-b)
(define region-a (rectangle->region rect-a))
(define region-b (rectangle->region rect-b))
(define a-intersection-b (intersection dc region-a region-b))
(send a-intersection-b is-empty?)))
#|Unfortunately this doesn't work-the is-empty? method only works on a
region% with an associated drawing context. Is there any way to salvage
this such that is-empty? can be used on region% objects unassociated with a
dc object? I'm not sure why they would require one, as otherwise the
region% interface seems fairly decoupled from the notion of
device-contexts. However, I'm sure that there is a reason that I don't yet
understand.|#
(define intersection
(lambda (region-a region-b)
(define new-region (new region% [dc a-dc]))
(send new-region union region-a)
(send new-region intersect region-b)
new-region))
#|The region documentation...
http://docs.racket-lang.org/draw/region_.html?q=region&q=any-of%3F#%28meth._%28%28%28lib._racket/draw..rkt%29._region~25%29._in-region~3f%29%29
I really just don't want to have to rewrite the overlaps? logic for my set
of shapes. Thanks all. |#
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